Acids react with metals to produce a salt and hydrogen gas. When hydrochloric acid, HCl, reacts with the metal zinc, Zn, the resulting salt is zinc chloride, ZnCl2. Chemists refer to these types of reactions as oxidation-reduction, or redox, reactions because electrons transfer from the zinc, which is oxidized, to the hydrogen atoms, which are reduced. Depending on the concentration of the acid, the reaction may proceed rapidly or slowly. Many college-level chemistry experiments involve reacting various metals with acids and then measuring the volume of hydrogen gas produced to determine the metal's atomic weight.
Instructions
1. Measure 5 mL of tap water into a 10- or 50-mL glass graduated cylinder. Add hydrochloric acid carefully to a final volume of 10 mL, while working in a well-ventilated area. This will result in a hydrochloric acid solution with a concentration of 6 moles per liter, which is the recommended concentration in college-level labs for reactions between metals and hydrochloric acid.
2. Place about 1 g of zinc metal in a glass container. Pour the 10 mL of hydrochloric acid from the graduated cylinder into the container containing the acid. The evolution of hydrogen gas should begin immediately. Swirl the container until all of the zinc has reacted.
3. Sprinkle baking soda into the container containing the acid solution slowly to neutralize the remaining hydrochloric acid prior to disposal. Carbon dioxide bubbles will immediately evolve from the solution. Continue sprinkling baking soda onto the solution and swirling the container until gas no longer evolves, at which point the solution is neutralized and you can safely pour it down a drain.
Tags: hydrochloric acid, acid solution, baking soda, container containing, container containing acid, container until
